1. Field of the Invention
The present invention relates to an apparatus for controlling chargeable batteries e.g., a secondary battery or the like, and an electronic apparatus provided with such a control apparatus.
2. Related Background Art
Portable electronic apparatuses and the like are generally equipped with a secondary battery, which can be repeatedly utilized by means of charging, so that the apparatuses may be driven by not only a commercial power supply but also the battery. Also, for example, in a printer or the like in which image is recorded on a recording material in accordance with image data transmitted from a host computer, it has been so arranged that the apparatus may be driven by not only a commercial power supply but also the battery as their miniaturization and weight reduction advance. Such a secondary battery is charged by a charging circuit built in the apparatus such as the printer, a charger for use in exclusive or the like. The charging circuit built in the apparatus is provided with a switching circuit for initiating or stopping the charge. The switching circuit is controlled in accordance with a level of a signal from an output port of a central processing unit (CPU).
FIG. 2 is a general arrangement of such a charge control circuit.
Referring to FIG. 2, in case of initiation of charge, when a signal on an output port of a CPU 200 is of high level, for example, a switching circuit 202 is operated so that a charging current flows from a charging circuit 201 to a secondary battery 203 and the secondary battery is charged. While, when the signal on the output port is of low level, the switching circuit 202 stops the charge operation of the charging circuit 201.
In this manner, according to the prior art, the start and stop of charge of the secondary battery is unequivocally determined in accordance with a level of the signal outputted from the output port of the CPU 200. Consequently, if it happens that the CPU 200 runs away for any reason, a level of the signal outputted from the output port is indefinite. Thus, it will be difficult to control the start and stop of charge of the secondary battery 203. In this case, there is no danger when the signal outputted from the output port CPU 200 is of low level. But if it maintains a high level state the secondary battery 203 falls into an over-charging condition, since the secondary battery 203 continues to be charged as long as a current is supplied from the charging circuit 201 thereto. This over-charging invites a problem that the lifetime of the secondary battery 203 is shortened, and also there is a danger that the secondary battery 203 heats excessively.
According to the above-mentioned printer, a process now in execution is interrupted in accordance with an initialization signal outputted from the host computer for initialization of the peripheral equipments so as to perform an initialization processing. Hence, if the initialization signal is entered from the host computer when the printer carries out a charging operation for the secondary battery, the printer interrupts the charging operation in mid course contrary to the operator's intention and performs the initialization processing. This results in a stand-by state in which the printer is receivably waiting for information to be transmitted from the host computer.